1. Field of the Invention
The present invention relates to an actuator provided with a motor and a wave gear reduction drive, and pertains to an actuator provided with an encoder for detecting the rotational speed or the like of an output shaft of the motor.
2. Description of the Related Art
A wave gear reduction drive has an annular rigid internal gear, a flexible external gear disposed on an internal side thereof, and a wave generator that causes the flexible external gear to flex in a radial direction and to mesh with the rigid internal gear, and moves meshing positions of both gears in a circumferential direction. In an actuator provided with the wave gear reduction drive, an output shaft of a motor is coaxially connected to the wave generator, and considerably reduced rotations are output in accordance with the difference in the number of teeth of both gears from the rigid internal gear or the flexible external gear.
In an actuator with this configuration, an optical encoder is mounted on the motor output shaft, and motor drive control is performed based on the output thereof, as disclosed in JP-A 2002-243000, for example. The optical encoder is coaxially mounted on an end portion of the motor output shaft, that is, on an end portion of the motor on a side opposite from the side to which the reduction drive is connected.
In an actuator provided with a wave gear reduction drive according to the prior art, a wave gear reduction drive, a motor, and an optical encoder are coaxially arranged in this order. Since these elements are coaxially arranged along the axial direction of the actuator, the entire length of the actuator is increased, and there are cases in which an installation location cannot be secured.